Comb copolymer consisting of poly (ethylene-co-vinyl alcohol) (EVAL) as backbone and poly (ethylene glycol) (PEG)
as side chains (EVAL-g-PEG) has been synthesized, then it was sulfonated by 1,3-propane sultone to get the final
ionomer (EVAL-g-SPEG), and ionic polymer-metal composite (IPMC) based on EVAL-g-SPEG was prepared through
electroless deposition of platinum onto the surfaces of EVAL-g-SPEG membrane. The graft copolymers were
characterized with respect to molecular weight using gel permeation chromatography (GPC) and composition using 1H-NMR.
The results showed that the No. of PEG graft of the side chains is n=1, 2 and others. Thermal properties were
examined by DSC and TG. The melt temperature (Tm) and glass transition temperature (Tg) of the comb copolymer
increase with the increasing length and the number of the side chains. Moreover, the deformation performance of IPMC
material was tested and its results show that the starting response voltage of IPMC actuator decreases with the increasing
IEC value. On the other hand, the starting response voltage increases with the decreased side chain length. The IPMC
with n=2 side chain length of PEG has the maximum tip displacement, and the maximum tip displacement of IPMC
membrane generally decreases with the side chain length of EVAL-g-SPEG. This feature may be the reflection of two
opposite effects, namely the decreasing ion densities and increasing water sorption of the membrane.
The ionomer of sulfonated ethylene vinyl alcohol copolymers (EVOH) modified by poly (ethylene glycol) (PEG)
(EVOH-g-SPEG) has been synthesized by the following process, EVOH was grafted by PEG through the Williamson
reaction and sulfonic groups were introduced onto the end of PEG side chain by the open ring reaction of 1,3-propane
sultone and the hydroxyl groups in EVOH. The crystalline structure and phase images of EVOH-g-SPEG membrane
were characterized by X-ray diffraction (XRD) and atomic force microscope (AFM), and the ion conductivity is
measured by a.c. impedance. XRD indicates that the water in EVOH-g-SPEG membrane region could destroy the
membrane crystalline structure and the water absorption membranes are nearly amorphous. AFM phase images of the
hydration membranes clearly show the hydrophilic domains, with sizes increasing from 10 to 35 nm as a function of the
side chain length and the phase inversion could also be observed when n≥5 (n, numbers of grafting PEG side chain),
which was consistent with a rapid increasing in water absorption. The a.c. impedance tests indicate that the comb-like
EVOH-g-SPEG grafting with 2 PEG side chain provides the highest ionic conductivity (1.65×10-3Scm-1). Moreover, the
tip displacement and the bending stress of ionic polymer-metal composites (IPMC) prepared by electroless deposition of
argentum were gained by electro-deformation tests. Its results show that the tip bending stress increased with the
increasing input voltage and reached to its maximum under the applied voltage of 3.6V~4.4V. IPMC based on the
EVOH-g-SPEG membrane exhibits higher bending stress with its maximum value of 6.20MPa.
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